The present invention relates to an electronic control system for a construction machine, and more particularly to an electronic control system for a construction machine comprising a prime mover, hydraulic equipment and systems, and a working device, the construction machine further comprising a plurality of control units divided for each function and at least one monitor unit for monitoring the status of the construction machine, the plurality of control units and the monitor unit being connected to each other for transmission and reception of data.
Recently, a keen demand has existed for an improvement of performance or a more variety of applications of a construction machine, particularly a hydraulic excavator as a typical example thereof, and electronic control has been progressed to cope with such a demand. In that situation, an electronic control system is required to be able to execute processing at high rate, and a control unit must be constituted using an advanced microcomputer, thus resulting in an increased cost. Also, with an increase in the number of input/output signals handled by a system, a control unit and a wire harness are complicated. To deal with those problems, distribution of control units is studied in which control functions of a hydraulic excavator are divided into individual unit functions, control units are provided in a one-to-one relation to the unit functions, and the control units are interconnected via a network for control of the entire machine.
For example, JP,B 7-113854 discloses an electronic control system for a hydraulic excavator, wherein control units are provided in a one-to-one relation to plural pieces of equipment, the control units respectively associated with the plural pieces of equipment are connected to a master controller via a common communication line, and the master controller performs integrated control of the entire system.
Further, JP,B 8-28911 discloses an electronic control system for a construction machine, wherein control units are provided in a one-to-one relation to plural pieces of equipment, and the control units are interconnected by a multiplex-transmission serial communication circuit to constitute a network allowing two-way communication for easier extension of the system. This publication also discloses an arrangement that a display monitor for displaying the operating status of the system is connected to the multiplex-transmission serial communication circuit.
Moreover, SAE Paper 941796 Development of Intelligent Hydraulic Excavatorxe2x80x94HYPER GX Series (issued in 1994) discloses an electronic control system for a hydraulic excavator, wherein control units are provided in a one-to-one relation to plural pieces of equipment, the control units ate interconnected via a network, and the network is divided into a low-rate network and a high-rate network (bus) for ensuring reliability of high-rate communication data.
On the other hand, in a construction machine such as a hydraulic excavator, monitoring functions are increasingly demanded, in addition to functions for control purpose, such as represented by recording machine operation data and monitoring the operating status for maintenance of a machine body, or displaying the status of a working device for assistance to operator work. For example, JP,A 7-110287 discloses a system for recording machine operation data in the compressed form and monitoring the operating status for maintenance of a machine body.
The above-mentioned prior-art control systems, however, have problems as follows.
In a construction machine, particularly a hydraulic excavator as a typical example thereof, the amount of data to be handled by a control unit and the update frequency (communication rate) of the data have increased with the progress of electronic control. Also, monitoring functions are increasingly demanded, in addition to functions for control purpose, such as represented by recording machine operation data for maintenance of a machine body, or displaying the status of a working device for assistance to operator work. Thus, not only the amount of data used for control, but also the amount of data used for monitoring has increased. When the above-mentioned prior-art control systems are employed in such a situation, there arise several problems described below.
In the distributed control system disclosed in JP,B 7-113854, the control units provided in a one-to-one relation to the plural pieces of equipment transmit all data to the master controller via the common communication line. The master controller processes those data in a batch manner, and then transmits control commands to the control units. If a monitoring function is added to that system, the amount of data communication between the control units and the master controller would be greatly increased because the master controller would have to handle all of control data and monitor data. Therefore, a common communication line capable of communicating data at high rate and a master controller capable of executing high-rate processing would be both required in order to prevent an adverse effect upon the control performance that should be considered with top priority. This would necessarily lead to more complicated construction of system equipment and a higher cost of the system.
Further, because of the control data and the monitor data being transferred via the same common communication line, if any trouble occurs in either data, communication would be no longer continued due to the mutual effect between both types of data, and the system would be stopped in the worst case. Particularly, the control system must be avoided from being stopped upon the occurrence of a trouble in the monitor data.
In the distributed control system disclosed in JP,B 8-28911, the control units divided for each function are connected to a single multiplex-transmission serial communication line for mutual communication. Therefore, the amount of data communication is probably not so increased in this system as expected in the distributed control system disclosed in JP,B 7-113854. However, because the control data and the monitor data are transferred likewise via the same common communication line, there still remains a problem that if any trouble occurs in either data, communication would be no longer continued due to the mutual effect between both types of data, and the system would be stopped in the worst case.
Further, the amount of data communication and the communication frequency via the multiplex-transmission serial communication line are set to be optimum for control in a situation where the control data and the monitor data are present in a mixed manner. Accordingly, if a new control unit (function) is added, the amount of data communication and the communication frequency would have to be set again for an increase in communication data. Hence, this prior art cannot be said as a system flexibly adaptable for addition of a new function. It is particularly important to avoid an increase in the monitor data from adversely affecting the control data.
In the distributed control system disclosed in SAE Paper 941796 Development of Intelligent Hydraulic Excavatorxe2x80x94HYPER GX Series, the network is divided into a low-rate network and a high-rate network. All control units of the system are connected to the low-rate network, which serves as a wide-area network. The use of the high-rate network is limited to the connection between the control units that require high-rate communication for the purpose of control. When adding a monitoring function to this system, however, control units for the monitoring are connected to the wide-area network because various kinds of monitor data must be handled. Consequently, as with the system disclosed in JP,B 8-28911, there accompany the problem of mutual interference between the control data and the monitor data, and the problem of insufficient flexibility for addition of a new function.
An object of the present invention is to provide an electronic control system for a construction machine, which has a control function and a monitoring function, and which can suppress an increase in the amount of data communication and the communication frequency via a single common communication line, and is flexibly adaptable for addition of a new function without causing mutual interference between control data and monitor data.
(1) To achieve the above object, the present invention provides an electronic control system for a construction machine comprising a prime mover, hydraulic equipment and systems, and a working device, the construction machine further comprising a plurality of control units divided for each function and at least one monitor unit for monitoring the operating status of the construction machine, the plurality of control units and the monitor unit being connected to each other for communication of control data and monitor data, wherein the electronic control system comprises at least two common communication lines including a first common communication line for communicating the control data and a second common communication line for communicating the monitor data; and the plurality of control units are connected to the first common communication line for communicating the control data among the plurality of control units via the first common communication line, and the monitor unit and a particular one of the plurality of control units are connected to the second common communication line for communicating the monitor data between the monitor unit and the particular control unit via the second common communication line.
By providing the first and second common communication lines such that a common communication line is divided into at least a line for control and a line for monitoring, the amount of communication data and the communication frequency are distributed to the two common communication lines, and an increase in the amount of data communication and the communication frequency via a single common communication line are suppressed. Therefore, a common communication line and a processing unit, which are capable of operating at extremely high rates, are not required, and individual pieces of component equipment can be avoided from being complicated and from having an increased cost.
Also, by dividing a common communication line into at least a line for control and a line for monitoring, mutual interference does not occur between the control data and the monitor data. Therefore, even if any trouble occurs in either control data or monitor data, both types of data are prevented from affecting each other. In particular, it is possible to prevent a machine body from being stopped upon a trouble occurred in communication of the monitor data.
Further, even if another monitor unit, for example, is additionally connected to the common communication line for monitoring for the purpose of function enhancement, the amount of communication data and the communication frequency to be handled via the common communication line for control are not affected, and the system is flexibly adaptable for addition of equipment.
(2) In above (1), preferably, the electronic control system further comprises a display device connected to the second common communication line and displaying the monitor data communicated via the second common communication line.
With that feature, the monitor data can be displayed to the operator without causing any influences upon the control performance.
(3) In above (2), preferably, the display device includes processing means for displaying the monitor data communicated via the second common communication line in graphical form.
With that feature, the displayed monitor data is more easily recognizable by the operator.
(4) In above (1), preferably, the electronic control system further comprises a display device connected to both the first and second common communication lines and selectively displaying the control data communicated via the first common communication line and the monitor data communicated via the second common communication line.
With that feature, not only the monitor data but also the control data can be displayed on the same display device. Even in a cab of a construction machine or the like having a relatively narrow space, therefore, it is possible to display the monitor data and the control data to the operator with a single unit of the display device. Also, since there is no need of installing the display device in plural number, the system cost is reduced.
(5) In above (4), preferably, the display device includes processing means for displaying at least one of the control data communicated via the first common communication line and the monitor data communicated via the second common communication line in graphical form.
With that feature, the monitor data and the monitor data can be displayed to the operator in a more easily recognizable manner.
(6) In above (4), preferably, the display device includes input means, generates a command signal for control and a command signal for monitoring in conjunction with contents of a display screen upon operation of the input means, transmits the command signal for control to a corresponding one of the plurality of control units via the first common communication line, and transmits the command signal for monitoring to the monitor unit via the second common communication line.
With that feature, both the control unit and the monitor unit can be operated from the display device, thus resulting in less intricacy in the operation.